The agent of non-A, non-B hepatitis continues to resist identification. A selected cDNA library was produced and screened for specific non-A, non-B hepatitis virus or disease related sequences, but none were identified. A second more highly selected library is presently being constructed. A cDNA expression library in Lambda gt 11 was constructed and screened with Dr. Shimizu's monoclonal antibody. No clones producing an antigen that reacts with the Shimizu antibodies have yet been isolated.